The present invention relates to the manufacture of tires. More specifically, it relates to the molding of the tread of such tires.
U.S. Pat. No. 5,492,669 describes a type of mold in which a great many metal sheets are arranged transversely to mold the tread. It is said here that the metal sheets, that is to say the molding elements, are oriented transversely because, when looking at the tire, they run from one of its shoulders to the other.
To open and close this type of mold requires coordinated movement, in a radial direction, of all the basic elements of the laminated peripheral ring. It is possible that the successive cycles of opening and of closing the mold will, in time, cause the metal sheets to become inclined with respect to their initial orientation, especially on account of parasitic friction responsible for misalignment or slippage of the metal sheets as they move while the mold is being opened and closed. Furthermore, it may prove difficult to maintain a distribution of inter-sheet clearances which is as even as might be desired. Molding flash may therefore occur in the places where the clearance between sheets has become markedly greater than the nominal clearance. Now, the desired objective is to choose the nominal clearance, as is explained in U.S. Pat. No. 5,492,669, specifically to prevent rubber from being able to run between the sheets throughout the mold-closure travel.
The objective of the invention is to overcome this drawback in order to improve the ability of a mold of this kind to mold tires with a high-quality appearance, especially with a quality of appearance which remains constant after many molding cycles.